3D-Mössbauer spectroscopic microscope for mc-Si solar cell evaluation

A 3D-Mössbauer Spectroscopic Microscope is developed to evaluate Fe impurities in multi-crystalline Si solar cells, which combines the Mössbauer spectroscopic microscope with a scanning electron microscope (SEM), an electron beam induced current (EBIC), an electron backscatter diffraction (EBSD), and an electron energy analyzer (HV-CSA). In addition, a new moving-coil-actuator with a liner encoder of 100 nm-resolution is incorporated for the operations with both a constant velocity and a constant acceleration mode successfully with the same precision as that obtained by the conventional transducers. Furthermore, a new multi-capillary X-ray lens is designed to achieve a γ-ray spot size less than 100 μm in diameter. The new microscope provides us to investigate the space correlation between Fe impurities and the lattice defects such as grain boundaries in multi-crystalline Si solar cells.     

Transformation of benzonitrile into benzyl alcohol and benzoate esters in supercritical alcohols

The reactions of benzonitrile in supercritical methanol, ethanol, and 2-propanol were investigated under non-catalytic conditions. In supercritical methanol, benzonitrile was converted to methyl benzoate in high yield. The esterification reaction also occurred in supercritical ethanol to afford ethyl benzoate in moderate yield. The esterification could occur via a route analogous to the Pinner reaction. On the other hand, benzonitrile in supercritical 2-propanol yielded no ester. Benzyl alcohol was the major product in supercritical 2-propanol. We investigated the reaction of the CN bond in supercritical 2-propanol. In supercritical 2-propanol, N-benzylideneaniline was transferred to the reduction product (N-benzylaniline) and hydrolysis products (benzyl alcohol and aniline). The hydrolysis reaction was restricted when the reaction was carried out in supercritical 2-propanol with a low water content. This indicates that the water in the 2-propanol acts as a reagent for the hydrolysis of the CN bond. These results suggested the following reaction process: C₆H₅CN→C₆H₅CHNH→C₆H₅CHO→C₆H₅CH₂OH.     

Novel continuous carboxylation using pressurized carbon dioxide by immobilized decarboxylase

Novel continuous flow carboxylation system was constructed using pressurized CO₂ at 6.5 MPa and immobilized enzyme, Bacillus megaterium PYR 2910 decarboxylase. The decarboxylase catalyzed the backward reaction, carboxylation, to convert pyrrole to pyrrole-2-carboxylate at the improved space-time yield by 25 times compared to the corresponding batch reaction.     

Synthesis and reactions of a stable 1,2-diaryl-1,2-dibromodisilene: a precursor for substituted disilenes and a 1,2-diaryldisilyne

Synthesis and isolation of the stable diaryldibromodisilene, Bbt(Br)SiSi(Br)Bbt, has been accomplished for the first time. The dibromodisilene underwent substitution reactions with organometallic reagents on the low-coordinated silicon atom to afford the corresponding substituted disilenes. Furthermore, the reaction of 1 with t-BuLi afforded the corresponding 1,2-diaryldisilyne, BbtSi[triple bond]SiBbt, the characters of which were revealed by spectroscopic and crystallographic analyses.     

X-ray diffraction analysis of photochromic reaction of fulgides: crystalline state reaction induced by two-photon excitation

Although most fulgides show their photochromism in the solid state, crystal structure changes accompanying the photochromism have not been previously observed. The photochromic reactions have been so far considered to take place on surfaces or at defects of the crystals or to proceed with destruction of the crystals. In this study we have succeeded in observing crystal structure changes accompanying the photochromism of fulgides using X-ray diffraction analysis. Detection of the photoproducts in the crystal structures was not possible when the single crystals of the fulgides were irradiated with steady UV light. Two-photon excitation by pulsed laser light was essential to produce a sufficient amount of the photoproducts without significant deterioration in the quality of the crystals.     

Rational tuning of the thiolate donor in model complexes of superoxide reductase: direct evidence for a trans influence in Fe(III)-OOR complexes

Iron peroxide species have been identified as important intermediates in a number of nonheme iron as well as heme-containing enzymes, yet there are only a few examples of such species either synthetic or biological that have been well characterized. We describe the synthesis and structural characterization of a new series of five-coordinate (N4S(thiolate))Fe(II) complexes that react with tert-butyl hydroperoxide ((t)BuOOH) or cumenyl hydroperoxide (CmOOH) to give metastable alkylperoxo-iron(III) species (N4S(thiolate)Fe(III)-OOR) at low temperature. These complexes were designed specifically to mimic the nonheme iron active site of superoxide reductase, which contains a five-coordinate iron(II) center bound by one Cys and four His residues in the active form of the protein. The structures of the Fe(II) complexes are analyzed by X-ray crystallography, and their electrochemical properties are assessed by cyclic voltammetry. For the Fe(III)-OOR species, low-temperature UV-vis spectra reveal intense peaks between 500-550 nm that are typical of peroxide to iron(III) ligand-to-metal charge-transfer (LMCT) transitions, and EPR spectroscopy shows that these alkylperoxo species are all low-spin iron(III) complexes. Identification of the vibrational modes of the Fe(III)-OOR unit comes from resonance Raman (RR) spectroscopy, which shows nu(Fe-O) modes between 600-635 cm(-1) and nu(O-O) bands near 800 cm(-1). These Fe-O stretching frequencies are significantly lower than those found in other low-spin Fe(III)-OOR complexes. Trends in the data conclusively show that this weakening of the Fe-O bond arises from a trans influence of the thiolate donor, and density functional theory (DFT) calculations support these findings. These results suggest a role for the cysteine ligand in SOR, and are discussed in light of the recent assessments of the function of the cysteine ligand in this enzyme.     

Fabrication and characterization of a novel inclusion complex of chiral monomer derived from (+)-camphor with beta-cyclodextrins

In order to develop a highly ordered polymer dopant to improve the physical properties of polymer materials for microsystems, a novel supramolecular inclusion complex (IC) of chiral bornyl 4-(6-acryloyloxyhexyloxy) phenyl-4'-benzoate ( BAPB) threaded with beta-cyclodextrins (beta-CDs) was synthesized. The inclusion complex was identified using Fourier transform infrared (FTIR), UV, 13C cross-polarization/magic-angle spinning (CP/MAS) NMR, 1H NMR, and X-ray diffraction (XRD). The construction of the fibrous self-assembled inclusion complex was confirmed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The highly ordered polymerized inclusion complex beta-CD-BAPB revealed significant birefringence and was confirmed using polarized optical microscopy (POM). Polymerization of self-assembled nanofibrous monomers with methyl methacrylate was carried out, and the distribution of the nanofibers in the polymer matrix was confirmed using POM. This investigation demonstrates a novel method for the fabrication of polymeric nanofibers with highly ordered, self-assembled functional monomers. The polymeric nanofibers are expected to improve the physical properties of polymer films in the field of microelectric and micromachine systems (MEMS).